There is an increasing demand for devices that can support multiple subscriptions, thereby supporting simultaneous wireless, e.g., cellular, access with different networks, such as different public land mobile networks (PLMNs) and/or networks operated by different carriers and/or different network operators. In order to support multiple subscriptions, devices, such as mobile terminals, may include multiple SIMs. In this regard, devices that include two SIMS are often referred to as dual SIM devices. However, devices may include any number of SIMs for supporting three, four, five or more subscriptions.
Dual SIM devices may permit consumers to reduce their call tariffs. In this regard, by utilizing the SIMs from two different operators on the same dual SIM device, the user is able to select the less expensive network for establishing an active connection. There are two principle types of dual SIM devices, namely, dual SIM dual standby (DSDS) devices and dual SIM dual active (DSDA) devices. DSDA devices may be utilized by users who desire to separate different contact groups. In this regard, a user of a DSDA device may provide one phone number associated with a first SIM to their business contacts and a different phone number associated with a second SIM to their private contacts since a DSDA device is able to receive a call to both SIMs regardless of other active connections.
In contrast to a DSDA device that permits the user to receive a call to both SIMs regardless of other active connections, a DSDS device having multiple subscriptions may allow all subscriptions to be registered to a wireless network, such as a cellular or other radio access network, but only one subscription can set up an active radio link toward the network at a time. In other words, a DSDS device generally has a single radio front end and base band chain. There are various subcategories of DSDS devices depending upon the status of the connection that another subscription can have toward the network while one subscription has an active connection toward the network. These subcategories range from DSDS devices in which a user manually selects the subscription that is to be active and registered to the network to DSDS devices in which the DSDS device interrupts an active packet switched connection, e.g., a data call, of one subscription in order to momentarily listen for pages in accordance with the other subscription.
In order to overcome some of the limitations of DSDS devices that have only a single radio front end and baseband chain, a DSDS device may include multiple, such as two, standalone cellular radios with each SIM connected to a respective cellular radio. In this context, a cellular radio may include the base band chain and the radio frequency hardware, as well as the software that controls the radio frequency hardware.
In an instance in which a DSDS device interrupts an active connection with a first network in order to read paging information from another network or to perform other procedures such as to perform tracking area updates or cell search procedures, a gap may be introduced into the active connection with the first network which may, in turn, negatively impact the communications conducted with the first network. For example, the gap in the reception from the first network may prevent the mobile terminal from promptly acknowledging and/or negatively acknowledging signals received from the first network, thereby preventing network downlink adaptation from functioning properly. Additionally, if the gaps introduced into the reception from the first network prevent the mobile terminal from transmitting signals in the manner requested or allocated by the network, network uplink adaptation may also not function promptly. Additionally, the gaps introduced by the reception from the first network may result in missed paging which may, in turn, cause the network to page the mobile terminal within a larger area, thereby increasing the paging load for several cells. Still further, the gap introduced in the reception from the first network may even cause the connection with the first network to be released.
In the idle state in certain networks, such as a universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN) or a global system for mobile communications (GSM)/Edge radio access network (GERAN), a mobile terminal may be allowed to interrupt the paging reception from the serving cell while reading system information for cell-reselection purposes. The carriers and radio access technology which should be evaluated by the mobile terminal for reselection purposes are signaled by the network. As such, an interruption in the paging reception as introduced by a DSDS device in order to read the system information of another network may also violate the current requirement specifications in an instance in which the other network has not been configured by the serving cell.
It may be difficult to predict the manner in which a network will interpret the gaps in reception introduced by a DSDS device in order to read paging occasions or system information of another network. However, a first network may interpret shorter gaps, such as gaps of tens of milliseconds, as a radio problem, while longer gaps may be classified as an error. As a result, the control algorithms, such as the algorithms for link adaptation, power control or the like, that are implemented by the network may be inaccurate. In other instances, there may be radio link failure and the initiation of corresponding recovery mechanisms. The challenges created by the gaps created in the reception from the first network by a DSDS device that reads paging occasions or system information from another network may not only impact the DSDS device, but may also negatively impact other mobile terminals supported by the same cell since the cell may experience decreased performance as a result of the network resources being consumed by the DSDS device. Additionally, the adaptation algorithms that are intended to optimize the network performance may also be inaccurate as a result of the gaps introduced to the reception from the first network by the DSDS device which may impact network performance and, in turn, the performance of other mobile terminals.
Multi-SIM devices may switch connections from network to network to use services more frequently than ordinary devices. Thus, there may be more connections breaks caused by multi-SIM devices and this type of use may cause inefficiencies in the network.